A phototube, or photoelectric cell, or photo-emissive cell, may be a sensitive detector of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum.
A photomultiplier tube (PMT) is a vacuum phototube that is able to multiply the current produced by incident light by many times, thus enabling individual photons to be detected when the incident flux of light is very low. Photomultiplier tubes have important applications in nuclear and particle physics, astronomy, medical diagnostics including blood tests, medical imaging, motion picture film scanning, radar jamming, and high-end image scanners known as drum scanners.
As shown in FIG. 1, a conventional PMT 100 includes a housing 101 containing a photocathode 102, several dynodes 104 and an electron collector 110. Light entering the tube 100 and incident on the photocathode 102 causes electrons to be emitted by the photocathode 102, as a consequence of the photoelectric effect. The electrons impinge on the successive dynodes 104, causing electron multiplication by secondary emission. After impingement on the last dynode, the electrons are collected by the collector 110 and used for detection of the incident light.
Although being widely used, the conventional PMT 100 is huge, heavy, fragile, expensive and difficult to produce.